1. Field of the Invention
The present invention relates to vehicular safety. More specifically, the present invention relates to a novel device for the equal distribution of inflation gases in an airbag cushion.
2. Technical Background
The inclusion of inflatable safety restraint devices, or airbags, is now a legal requirement for many new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield. Side impact airbags, also known as inflatable curtains, have been developed in response to the need for similar protection from impacts in a lateral direction, or against the side of the vehicle.
Despite their enormous lifesaving potential, the effectiveness of side impact airbags has been somewhat limited by the speed with which inflation gases are able to fill the cushion. Side impact cushions are often designed to unfold or unroll downward to inflate beside a person to keep the person from hitting the door or window during lateral impact. Since a vehicle occupant may be leaning forward, reclined in the seat, or at any position between, such cushions are often made somewhat long to ensure that the occupant hits the cushion.
Cushions for inflatable curtains are often inflated by an inflator positioned either fore or aft of the cushion. Consequently, unlike many front impact airbags, a long gas flow path exists between the inflator and the outermost extent of the cushion. The length of the gas flow path is problematic for a number of reasons.
One such reason is that the cushions are unable to inflate rapidly enough to provide optimal protection. Since most airbag systems are unable to detect a collision until impact has begun to occur, the airbag must move from an uninflated, stowed configuration to a fully inflated configuration within a small fraction of a second. The long flow path increases the time required by the inflation gases to traverse the cushion. Thus, the cushion may not obtain a fully inflated state before the vehicle occupant strikes the cushion.
In an attempt to compensate for the longer gas flow path, inflators with a higher “rise rate,” or rate of pressure increase of expelled gases, and a higher volume of expelled gases, have been used. Unfortunately, when the inflation gases are more highly pressurized, there is a higher danger of damage to the cushion. Highly-pressurized gases produce stresses in the material of the cushion that may tend to rip the cushion material or split the cushion open along the seams, thereby jeopardizing the effectiveness of the cushion.
Furthermore, even when the inflator produces a larger amount of gas, the inflation gas may expand in the portion of the cushion nearest to the inflator, rather than continuing toward the furthest extents of the cushion. As a result, the cushion may not be uniformly inflated in time to properly shield occupants from impact.
Existing airbag configurations developed in an attempt to solve this problem also have some drawbacks. Some are difficult and/or expensive to manufacture, in part due to additional drilling, punching, aligning, fixturing and the like that must be carried out. Some increase the expense of airbag installation because they have parts that must be inserted into a finished cushion prior to installation of the cushion in a vehicle. Others require additional time to reach a steady state after inflation due to backflow and other continued motion of inflation gases within the cushion.
Currently available side impact airbag cushions are generally designed to protect only the passengers of the front seats and the seats directly behind the front seats. For example, in a vehicle with three seating areas such as a minivan or sport-utility vehicle, the side impact cushion only has protection zones for the front and middle seats. The occupants of the rear seat are not protected by the airbag cushion.
In an airbag cushion designed to protect passengers all three seating areas there may be a problem with uniform inflation of the cushion. Generally, long airbag cushions are inflated by a single inflator. Using a single inflator for all protection zones costs less than using multiple inflators for the cushion. Moreover, the use of one inflator reduces the risk of airbag malfunction. However, because the airbags use one inflator, there may be unequal pressure buildup in the protection zones. The pressure buildup can cause the cushion to inflate in a non-uniform manner.
Accordingly, a need exists for a side impact airbag cushion configured to protect occupants of all seats of a vehicle. In particular a need exists for an apparatus that can provide side impact protection for the occupants of the front, middle, and rear seats of a vehicle. Additionally a need exists for an apparatus and method for distributing inflation gases in an inflatable cushion in a comparatively uniform and rapid manner. A need further exists for such an apparatus and method that can be carried out with a minimum of added expense to the manufacture and installation of the cushion. Furthermore, a need exists for such an apparatus and method that is capable of rapidly equalizing the pressure within the protection zones of the airbag cushion.